A VSC position tracking system involving a large scale pneumatic muscle actuator

A variable structure controller (VSC) is developed to provide position tracking capability for a very large pneumatic muscle actuator, which has inherently nonlinear dynamics. After the controller design is completed, the internal dynamics of the closed-loop system are shown to be stable. Robustness and passivity issues are then discussed. The switching law is modified to account for the different dynamics through the use of a composite Lyapunov function which guarantees asymptotic tracking stability.